1. Field of the Invention
The present invention relates to a tilt-trim system for use with an outboard motor to be mounted on a boat.
2. Description of the Relevant Art
Small ships such as motor boats or the like are associated with a tilt-trim system. The tilt-trim system comprises a tilt cylinder unit for swinging a swivel bracket through a large angle to lift the lower portion of the outboard motor above the water level or lower below the water level, and a trim cylinder unit for angularly moving the swivel bracket through a relatively small angle to trim the outboard motor while the lower portion thereof is being submerged.
According to the general tilt-trim system design, two trim cylinder units are disposed one on each side of a single tilt cylinder unit. The tilt cylinder unit has a piston rod pivotally supported on a swivel bracket through an upper shaft, and a cylinder pivotally supported by an under shaft on a stern bracket attached to the boat. The trim cylinders, which are separate from the tilt cylinder, are mounted on the stern bracket. A manifold containing a hydraulic pressure pump is mounted on one of the trim cylinders, and a motor for actuating the hydraulic pressure pump is mounted on the manifold. The manifold and the tilt cylinder are connected to each other by external lower and upper pipes.
Since the tilt and trim cylinders are separate from each other and the manifold is integrally mounted on one of the trim cylinders, at least two hydraulic pressure pipes, i.e., the lower and upper pipes, for interconnecting the manifold and the tilt cylinder have to be installed exteriorly on the manifold and the tilt cylinder. However, inasmuch the tilt cylinder is swung when the outboard motor is tilted upwardly and downwardly, the hydraulic pressure pipes are fatigued due to repeated bending, and tend to rust owing to galvanic corrosion. The manifold is subjected to shocks through the under shaft and the tilt cylinder when the outboard motor is hit underwater by foreign matter such as driftwood. Consequently, the manifold must be mechanically strong enough to withstand such shocks, and hence is large and heavy.